1. Field of the Invention
The present invention relates to a method and apparatus in which a terminal transmits channel information for at least one serving cell to a base station in a wireless communication system, and more particularly, to a method and apparatus for transmitting and receiving periodic channel information in a wireless communication system.
2. Description of the Related Art
Generally, mobile communication systems have been developed to provide voice services, to allow for mobility of a user. Mobile communication systems have expanded data services as well as voice services, and now, they are capable of providing high-speed data services. However, in mobile communication systems which currently provide services, due to a shortage of resources and user's demands for higher-speed services, mobile communication systems are required which are further developed.
To meet such demands, standardization work on Long Term Evolution (LTE), one of the next-generation mobile communication systems, is in progress in the 3rd Generation Partnership Project (3GPP). LTE implements high-speed packet-based communication at a data rate of up to about 100 Mbps. To this end, various schemes have been discussed, such as a scheme for reducing the number of nodes located on a communication path by simplifying a structure of a network and a scheme for arranging wireless protocols close to wireless channels.
In 3GPP LTE release-10 (rel-10), to support higher data transmission quantity than LTE rel-8, a bandwidth extension technique has been adopted. Bandwidth extension, also called Carrier Aggregation (CA), may extend a band, thus increasing data transmission quantity by the extended band when compared to an LTE rel-8 terminal for transmitting data in a band. Each band is called a Component Carrier (CC), and the LTE rel-8 terminal is prescribed to have one CC for each of a Downlink (DL) and an Uplink (UL). UL CCs, which are SIB-2 connected with DL CCs, are called a cell. The SIB-2 connection relationship between the UL CCs and the DL CCs is transmitted as a terminal-dedicated signal. A terminal which supports CA may receive DL data and transmit UL data through multiple serving cells.
When a base station has difficulty in sending a Physical Downlink Control CHannel (PDCCH) to a particular terminal in a particular serving cell in LTE rel-10, it transmits the PDCCH to the terminal in another serving cell and sets a Carrier Indicator Field (CIF) as a field for indicating that the PDCCH indicates a Physical Downlink Shared CHannel (PDSCH) or a Physical Uplink Shared CHannel (PUSCH) of the another serving cell. The CIF may be set in the terminal which supports CA. The CIF is determined to indicate the another serving cell by adding 3 bits to the PDCCH information in the particular serving cell. The CIF is included only when cross carrier scheduling is performed. If the CIF is not included, cross carrier scheduling is not performed. When the CIF is included in a DL assignment, the CIF indicates a serving cell in which the PDSCH scheduled by the DL assignment is to be transmitted. If the CIF is included in a UL grant, the CIF is defined to indicate a serving cell in which the PUSCH scheduled by the UL grant is to be transmitted.
As such, in LTE rel-10, the bandwidth extension technique CA is defined, such that multiple serving cells may be set in a terminal. For data scheduling of the base station, the terminal periodically or aperiodically transmits channel information for the multiple serving cells to the base station.
In LTE rel-11, a maximum of five serving cell setting scenarios are assumed, and in this case, channel information transmission for multiple serving cells in one sub-frame may collide with each other. Thus, a need exists for a method for supporting an operation of the terminal such that channel information for as many serving cells as possible may be periodically transmitted in one sub-frame.